National Fiber Cellulose Insulation The Natural Choice for High Performance Green Building
Consumers and builders have many choices when it comes to what type of insulation to use
in their new home. Cellulose, fiberglass, and foam insulations are the most readily available
options. Insulation decisions are typically based on performance, value, and environmental
aspects.
Your insulation choice not only includes its thermal performance (R-Value), but should also
include its fire resistance, sound blocking capability and resistance to mold, insects, and
vermin. In terms of thermal performance, R-value is not always the best indicator of how the
insulation will perform in your home. R-values are measured in the laboratory and don’t take
into account the effects of wind and pressure differences within the home caused by the
height of the home (Stack Effect), and mechanical systems such as dryers, range hoods, and
heating and cooling equipment. When these pressures are coupled with the fact that homes
are built from thousands of pieces, all with edges joints and gaps (also known as holes!), it
means that air will try to move through and around your insulation.
Insulation works by trapping air between its fibers or pores. It is this trapped air and not the
wood or glass fiber that provides the resistance to heat flow. When air flows through or
around your insulation, your insulation loses its effectiveness, leading to an uncomfortable
home and high fuel bills. Conventional fiberglass performs poorly, since air moves through it
very easily, and it has unsealed edges and gaps no matter how well it is installed. Cellulose
insulation, whether it is sprayed into a wall assembly or injected dry, i.e., ‘dense packed’, at
densities of 3.5 pounds of material per cubic foot (lbs/cf), blocks air movement and leaves no
gaps or joints for air to flow through. This means that cellulose delivers a consistent
performance of R 3.8 per inch for cellulose. At these high densities, the cellulose insulation
will also remain stable and in place, with no settling, for the life of the structure.
The other reason for blocking air movement is that air accounts for over 98% of moisture
movement in a structure. Thus, if we block the flow of air, we eliminate the potential rot and
damage, and prolong the life of the structure. But what about vapor barriers?
Cellulose insulation has been installed in millions of homes and buildings successfully since
the 1920’s without vapor barriers. The hygroscopic nature of the cellulose means that any
moisture entering is dispersed and slowly diffuses through the material without accumulation
or damage, protecting both the insulation and the surrounding materials. Fiberglass
insulation has no moisture storage capacity. Moisture easily passes through fiberglass,
condensing on the interior or exterior sheathing (depending on the season), causing
deterioration of the structure. The hydrophobic properties of foam are very protective to the
material, but offer no protection to the surrounding materials.
50 Depot Street • Belchertown, MA 01007 • 800-­‐282-­‐7711 • w ww.nationalfiber.com A house fire is something we all want to avoid. In terms of fire resistance, cellulose insulation
is superior to other insulation options. Laboratory testing has shown that 14.5 inches of
cellulose outperforms wood fire blocking. The boric acid fire retardants prevent flames from
traveling through the cellulose and enhance the fire resistance of any assembly that cellulose
is used in. Fiberglass insulation doesn’t burn, but it melts when exposed to flame, allowing
fire to spread vertically very quickly. Foam insulation burns when exposed to fire and
releases large quantities of toxic smoke.
The borate based fire retardants used in cellulose insulation also help discourage mold,
insects and vermin. Borates are derived from naturally occurring borax and are permanently
impregnated into the cellulose fibers. Fiberglass and foam insulations do not offer the same
protection.
As buildings continue to be built in closer proximity and next to busy roads, the sound
performance of your insulation becomes more important. Cellulose insulation offers the best
sound blocking capability of any insulating material, due to its high density, air blocking
ability, and vibration dampening qualities. In a 2x4 wall, cellulose achieves a sound
transmission coefficient (STC) of 41, blocking out normal conversation and noise.
The environmental aspects that are important in selecting your insulation include recycled
content, embodied energy, and local production and manufacturing. Cellulose insulation is
made from recycled newspaper and has a recycled content of over 82%. Fiberglass may
have up to 35% recycled glass and foam insulation between 0 to 9% recycled content to its
petrochemical formulation. The amount of energy that it takes to manufacture the insulation
(embodied energy) also varies widely. Cellulose insulation is produced in regional
manufacturing facilities using 750 Btu/lb of material produced. Fiberglass takes 12,000
Btu/lb to heat and process the glass, while foam insulation uses 30,000 to 48,000 Btu/lb to
manufacture from petroleum based chemicals. Both are produced in large, centralized
manufacturing plants.
The value of your insulation depends not only on your initial price, but also on what your
insulation choice will cost over a period of time in heating and cooling bills. Fiberglass has
the lowest initial price, but it will end up costing much more over time in higher heating and
cooling bills and reduced comfort. Foam insulation has good thermal performance, but it has
a much higher initial cost compared to the other options. Foam also has limitations in terms
of sound attenuation and smoke production in the event of a fire, and is not the most
environmental choice you can make. The cost of cellulose insulation typically falls between
fiberglass and foam, while exceeding both of them in terms of performance and
environmental friendliness. Cellulose insulation is not only the green choice, but it is also the
best choice when performance and comfort are desired.
For further information, please contact our Technical Manager, Bill Hulstrunk, at
[email protected].
50 Depot Street • Belchertown, MA 01007 • 800-­‐282-­‐7711 • w ww.nationalfiber.com